Polymer-capped silver nanomaterials are emerging as eco-safe alternatives for phytopathogen management. In this study, chitosan-coated silver nanoparticles (Ch-Ag NPs) were synthesized via a green sonochemical method using Calotropis procera leaf extract as a natural reducing agent. Chitosan functionalization enhanced nanoparticle stability, bioavailability, and safety.

Structural and elemental analyses confirmed the formation of phase-pure crystalline Ag⁰ with a face-centered cubic structure and preserved polymer integrity. Ch-Ag NPs exhibited strong antibacterial activity against Ralstonia solanacearum and Pseudomonas syringae pv. tomato, producing inhibition zones of 22.5–25.5 mm, significantly higher than the crude plant extract. Greenhouse experiments were conducted on tomato (Solanum lycopersicum) plants inoculated with P. syringae pv. tomato to evaluate nanoparticle–plant interactions under pathogen stress. Beyond antibacterial effects, Ch-Ag NPs induced a concentration-dependent hormetic response. Low to moderate doses (5–10 mg L− 1) enhanced chlorophyll content and stimulated phenolic and flavonoid biosynthesis via controlled H2O2-mediated signaling, accompanied by upregulated expression of antioxidant (SOD, CAT, APX) and defense-related (PAL, CHS, PR1) genes, indicating metabolic priming. In contrast, higher concentrations (≥ 15 mg L− 1) disrupted redox balance, causing oxidative stress, chlorosis, and metabolic inhibition due to excessive Ag+ release and thylakoid damage, as supported by nutrient imbalance data. Overall, Ch‑Ag NPs act through a dual, dose‑dependent mechanism combining effective pathogen suppression with beneficial metabolic conditioning.

This study uniquely integrates green sonochemical synthesis, antibacterial evaluation, and plant physiological–molecular analyses to define an optimal hormetic dose window for Ch‑Ag NPs application in S. lycopersicum under bacterial pathogen stress, highlighting their potential as environmentally friendly nano‑pesticides for sustainable S. lycopersicum production.

Aghamir, Fateme & Alvand, Zinab & Farzaneh, Mohsen & Alvand, Tayebeh. (2026). Chitosan‑capped silver nanoparticles trigger hormetic defense responses and gene expression changes in Solanum lycopersicum L.. BMC Plant Biology. 10.1186/s12870-026-09982-w.

Source: ResearchGate




Frontpage photo:
© Swkunst | Dreamstime




Publication date:

Thu 1 Oct 2026